Justin Rose ensured that golf made an instant impact on its return to the Olympic Games after his hole in one lit up the opening round in Rio.
Marcus Fraser of Australia, who produced some superb golf on the Gil Hanse designed course carved into the Marapendi Nature Reserve.
But Open champion Henrik Stenson is the Australian's closest challenger along with Graham DeLaet, while Rose is a shot further back after a 67 which included the shot of the day at the par-three fourth.
Brazil's Adilson da Silva had to control his nerves when he hit what he called the biggest shot of his life - teeing off on Thursday to mark golf's return to the Olympics.
Fraser shot 8-under 63 on the Gil Hanse-designed course to take a three-shot lead over British Open victor Henrik Stenson and Canadian Graham DeLaet heading into Friday's second round of the 72-hole, individual event.More news: Ukraine denies attempted armed invasion of Crimea
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"If I had played the last three holes right I would have come in two or three under and have a totally different feel".
On the first round of golf at an Olympics saw the Irish duo post a 70 and 71 respectively. And as the only Brazilian in the men's competition, he was chosen to hit the opening tee shot at Olympic Golf Course. He explained "very rarely are you in one place with so many like-minded people who are there to give 100 per cent and constantly better themselves to try and extract their peak performance on a given week". Rose climbed up the leaderboard to three under par in the first round, one ahead of Team GB team-mate Danny Willett.
"The atmosphere was great", said Harrington.
"Teeing off in particular, I think I was the first American to tee off today", Kuchar said.
Speaking to reporters after he carded a one over par 72 in his first round, da Silva broke down in tears recalling how as a child, he fashioned homemade golf clubs out of tree branches. Most weeks there are 156 players and only one victor.